Field of the Disclosure
The present disclosure relates to an organic light-emitting diode display device, and more particularly, to an organic light-emitting diode display device capable of improving light efficiency and a color gamut and a method of fabricating the same.
Discussion of the Related Art
Recently, flat panel displays have been widely developed and applied to various fields because of their thin profile, light weight, and low power consumption.
Among the flat panel displays, organic light-emitting diode (OLED) display devices, which can be referred to as organic electroluminescent display devices, emit light during loss of electron-hole pairs. Typically, the electron-hole pairs are formed by injecting charges into a light-emitting layer between a cathode for injecting electrons and an anode for injecting holes.
The OLED display devices may be formed on a flexible substrate such as plastic. Because they are self-luminous, the OLED display devices generally have excellent contrast ratios. The OLED display devices typically have a response time of several micro seconds, and there are advantages in displaying moving images. In addition, the OLED display devices typically have wide viewing angles as they are self-luminous.
OLED display devices are generally divided into passive matrix type OLED display devices and active matrix type OLED display devices according to a driving method. Active matrix type display devices, which typically have a low power consumption and a high definition, are widely used. In addition, the size of active matrix type display devices may be large.
An OLED display device often includes a plurality of pixels, each of which includes red, green and blue sub-pixels. The red, green and blue sub-pixels include red, green and blue organic light-emitting layers, respectively. Red, green and blue lights emitted from the sub-pixels are mixed to produce an image.
The red, green and blue organic light-emitting layers are typically formed of different materials and have different properties. Because of this, the red, green and blue sub-pixels have different light efficiencies and different lifetimes, which may lead to problems. To solve such problems, an OLED display device including color filters has been suggested.
In such a solution, each pixel typically includes red, green and blue sub-pixels, and each of the red, green and blue sub-pixels includes an organic light-emitting layer emitting the same color light. For example, the organic light-emitting layer of each of the sub-pixels emits white light. The red, green and blue sub-pixels further include red, green and blue color filters, respectively. Therefore, the white light emitted from each sub-pixel passes through the red, green and blue color filters, and red, green and blue lights are outputted. The red, green and blue lights are mixed to thereby produce an image. At this time, to express exact colors, it may be necessary to match colors of the white light emitted from the organic light-emitting layers and the color filters.
Particularly, color filters have been widely used for liquid crystal display (LCD) devices. But white light emitted from a light source for an LCD device has red, green, and blue peaks and band widths different from the white light emitted from the organic light-emitting layers of an OLED display device. Thus, there may be a problem of low color gamut when general color filters, such as those used for LCD devices, are applied to an OLED display device. Also, because the color filters absorb light having different wavelengths, light efficiencies are decreased.
Meanwhile, to increase the color gamut and the light efficiency of the OLED display device including color filters, a structure including a color changing layer on the color filters has been suggested. The color changing layer absorbs short wavelength light and emits long wavelength light. Different color changing patterns are typically formed on the red, green and blue color filters. That is, a red color changing pattern may be formed on the red color filter. A green color changing pattern or a yellow color changing pattern maybe be formed on the green color filter. A blue color changing pattern or no color changing pattern may be formed on the blue color filter.
Therefore, the OLED display device including the color changing layer may need at least two photolithography processes in order to form the different color changing patterns on the different color filters. The photolithography process for pattering a thin film may include a plurality of steps of coating a photosensitive material, light-exposing the photosensitive material using a mask, developing the photosensitive material, curing the photosensitive material, and so on. Thus, the OLED display device including the color changing layer may have a wide color gamut, but its manufacturing time and costs are increased.